You need a license for qt-creator if you want to work on commercial software (or that was the case last time we checked about a year or two ago). There might be exceptions for your case, do check, because it is a nice product. Other paid IDE alternatives are CLion, which I hear is excellent, as well as SlickEdit, which is closer to an editor than a full IDE, but does offer building, debugging, completion.

Free alternatives would be Visual Studio Code, which is pretty ok even for C++, or KDevelop, which almost kind of works, or SpaceVim / SpacEmacs and about a week of learning how to use it. I'm in the final camp, since basically every serious C/C++ dev on Linux has a Vim or Emacs setup they've built themselves that does about 90% of what Visual Studio gives you out of the box, with some things better and others worse. It can work pretty well, but you have to understand it's not VS and it works in its own way.

If you have the money, you can buy a good IDE for Linux. Otherwise, learning to make your own out of high-level building blocks is also a useful skill, but takes a little bit of time. Personally the first time I had to write C for Linux out of college it did take me about a week before I was up to speed with it (but I was already sort of familiar with vim as a pure editor).